Dry manganous phosphate compounds



Dec. 30, 1958 w. D. WARINNER DRY MANGANOUS PHOSPHATE COMPOUNDS 2 Sheets-Sheet 1 Filed April 30. 1956 ON @Avon 5:2

NANIV ouw .LHSIEM Afa Z INVENTOR WARREN D. WARINNER BYGa/mm,mwn

ATTORNEYS Z Mno BY WEIGHT Dec. 30, 1958 W. D. WARINNER DRY MANGANOUS PHOSPHATE COMPOUNDS Filed Aprill 30. 1956 LEGENDI POINT CITED FROM LITERA COMPOSITION PREPARED AND EVALUATED OF HYDRATION` CONCENTRATION CONSTANT MnO-F2 so 55 Z P205 BY WEIGHT 2 Sheets-Sheet 2 WARREN D. WARINNER 8%,1/M/a/msuzw ATTORNEYS hcc 2,866,723y DRY MANGANoUs vPr'IosPHATls CoMPoUNDS Warren D. Warinner, ICollege Park, Ga., assignor to Tennessee Corporation, New York, N..Y., a corporation of New York Application April 30, 1956, Serial No. 581,586 7 Claims. (Cl. 148.-6.15)

This invention relates to no vel dry substantially com. pletely water-soluble manganous phosphate compounds and more particularly to such compounds comprising mole to one mole of orthophospho/ri.` acid per mole of manganous dihydrophosphate and one-half to two and one-half moles of water of crystallization.

ticularly still this invention relates to such pounds are to be dry within the concept of the present of two' and one-half moles of water of crystallization is required.

It has heretofore been proposed to coat metal surfaces with adherent insoluble manganese phosphate films by dipping or by otherwise treating the metal surfaces with manganese in solution. Solutions of manganese in phossuitable for the preparation of lmanganous phosphate coating baths.

Another object is to provide such novel"compounds which exhibit negligible loss due to hydrolysis when used in the preparation and reconstitution of coating baths.l` Another object is to provide such novel compounds which are substantially completely water-soluble. v

Another object is to provide such novel compounds containing available phosphoric acid to maintain a balanced solution in the coating bath.

Another `object is to provide such novel compounds having a higher phosphoric acid ratio to manganese than in mangano-us compounds now in use.

Another object is to provide such novel dry manganousy phosphate compounds which, when'in solution, will coat metals more uniformly with a thicker coat of manganese phosphate requiring less of the manganese phosphate as the coating material.

Another object is to provide such novel compounds which have ratios of manganese to phosphoric acid heretofore available only in solutions.

Another object is to provide such novel compounds which may be Vadjusted in composition to suit a variety of requirements.,

Another Objectis to provide orthophosphori acid in anon-liquid'rea'dily transportable form.

Other and further objects of the present invention will appear from the following description of illustrative embodimentsI thereof.

I have found that the'novel dry manganous phosphate compounds of this invention, having the yphysical characteristics and advantages described in these objects, have a MnO to P205 to H2O' percentage'ratio o f approximately 23.3-1v8.0% MnO; 6 O.7-51.6% P205; and` 28.1-18."/`%` H2O and have a molar ratio ofone-half to one mole of orthophosphoric acid per mole of manganous dihydrof phosphate and havevfrom one-half to two and one-half moles-of water of crystallization.. It is therefore apparent that a family of dry manganous phosphate rcompounds come within the purview of the present` inventive concept and thatthe illustrative embodiments thereof discussed phoric acid are known in the art, for example, manganous l I dihydrophosphate dihydrate. Studies of the systems MnO-P2G5H2O have beenl published byV M. Amadori, Y l

Atti. ist. Venito, 8l, 60S-17 (1921-22); in the article by Grube and Staesche, Z. physik.y Chem., 13.0; "5772-583 (1927); and in thearticle by Taperova and lsaeva, I. Applied Chem. (USSR) 22, 34253 (1949). United States patents have issued in'this'eld including*'WillardmgS5 No. 1,660,661; Green No. 1,651,694;` Booth No. `2,031,- 579; and Maclntyre No. 2,993,461. M l The dry manganous compounds known to the prior art are discussed 1n these articles and patents have .cer-V tain undeslrable characteristics, the most importantqof which is leither excessive loss of manganese phoric acid fromthe'coating solution by hydrolysis which takes place Iboth in the preparation'ofthe bathand inreconstitution of theA present invention dry manganous phosphate compounds below can in no way be construed as delining or limiting the invention. Reference should therefore lbe had to the appended claims to determine the scope of the present inventive concept.

The

solubility-isotherm-phase diagram for MnO-P2O5-H2O .wherethe percentage of water is-inferred as the difference between 1.00% andthe sum of the percentages 'o fMnO and P205 at25 C., the range of the compounds ofithe present inventionbeing shown in the area n, b, c, d; and

Fig. 2 is an enlargedy detail of a portion of Fig. l ,Shaving the fangs 0f the Compounds Qf .th

lventionu and showing representative compounds within the area 'of the present invention.

The dry manganous phosphate compounds of the present inventiO-n are prepared without requiring'fracitional crystallization by the addition ofv aslurryfof manganous :ion donor to a concentrated solution of phosphoric acid containing suicient hydrogen peroxide to assure maintenance of the manganous state. No extermal heat need Vbe applied to the reaction and,.up,on completion of the reaction., the resultant liquor may 'be:clarified if necessary and then dehydrated as rapidly -as possible to the desired degree of dehydrationer l More particularly, these novel dry manganous phosp'hatel :compounds are preferably prepared by adding either a slurry of manganous carbonate or dry man- Patented Dec. 3,0, llliat c ompound to recon?.k stitute the solution after use and which will yield more ganous carbonate to phosphoric acid starting at ambient temperatures and applying no external heat during the reaction. Suitable manganous phosphate solutions are assured when a small amount of H2O2 is added to the phosphoric a'cid `before the. manganousv carbonate` is added to the acid. About .6 113.11202 per 100 lbs."of manganese `assures `proper control of the reaction and the production of` he solutions. Any excess H2O2 is driven ofi during `subsequent concentration of the solution at about 60.C. The use of H2O, in a reaction of this type is discussed in British Patent No. 447,918`granted in 1936.

It is highly desirable "to avoid the" precipitation ot crystalline material from' the initial liquors previous to the, starting of evaporation for practical as well of insoluble pyrophosphates and/or metaphosphates appears to be more a function of time than of temperadesired 'manganous phosphate t ture, generally occurring during the trans1tion from the hemihydrate to the anhydrous state. Drying temperatures up to 260 F. are preferred.

The use of manganous carbonate is preferred in forming the original slurry as the resulting manganous phosphate solution does not require filtering and impurities are not introduced into the solution as is the case when other sources of manganese are used.

The dry manganous phosphate compounds shown at points a, b, c and d of Figs. 1 and 2, defining the limits of the family of compounds of the present invention, are made by the'procedures described above and have compositions as described in the following table:

TABLE I Composition Weight Ratios Sample Point Perg Perg Per;l Perg 1 ?205 P205 P205 Mn MnO H10 cen cen cen cen T' T Mn MDO P H2O itin M110 H2O P.Os P Os i P205 1.5.7 20.4 51.6 28.0 3.287 2.529 1.843 0.304 0.395 0. 543 17. 9 23. 3 57. 7 19. 0 3. 224 2. 476 3.037 0.310 0. 404 0.392 15.84 20.46 60. 7 18. 8 3. 832 2. 007 3. 229 0. 261 0.337 0. 309 13. 9 18. D 53. 9 28. 1 3.878 2. 094 1. 918 0. 25S 0. 334 0.521

as technical reasons and I have found that the best results are obtained by liming the maximum concentration of the initial liquors to between 9.6% and 10.8% MnO and 29.0% and 27.5% P205 by, weight; this practice defers the appearance of' crystals during evaporation until a considerable amount of concentration has been realized and promotes the `formation of very iine crystals which subsequently recrystallize to the desired compositions.

After the desired manganous phosphate solution is obtained approximately two-thirds of the excess water is removed to form a slurry and'the iinal dehydration of the thickened slurry should be accomplished as quickly as` possible to avoid the formation of pyrophos phates or the solution may be dehydrated in one step by other methods such as spray drying. The formation The compounds identiiied at points a, b, c and d in Figs. l and 2 and as described in Table I are substantially completely soluble in cold water; they do not hydrolyze; and they have the desired physical characteristics that allow dry packaging without agglomeration. These compounds also withstand pressure without permanent coalescence. l

Various dry manganous phosphate compounds within the limits deiined by points a, b, c and d of Figs. 1 and 2 and having the desired characteristics described above with respect to the compounds of Table l are shown and described in the following tables which compare these compounds with known compounds, the illustrative compounds of the present invention being identied by numerals 10, 11, 12, 13 and 14:

TABLE Il Solid Materiels Used Initial Solution Alter Dlgesting Gms. Solids Wt. ratio, Etf. oi Composition, P10; Composition, Pointage Pointage Solids Manganous Percent "'Mno Grns. Gm./L. Equiv. vs. Phosphate Solids Total to 1.0 Ale. Compound perA Free per gm. Wash. Liter point, Ale. Dihyiiter Wash. dro. Mn MnO P10; Actual Thteo Mn MnO P10; pH Free Total pH Free Total Ddirhyre o. 10 16.6 21.4 54.0 3. 254 3.230 Z) 3. 32 4.28 10.8 2.53 2.6 22.0 2. 47 2.8 21.8 7.8 0 910 0 806 124.1 l1 16. 5 21. 3 55. 5 3. 364 3. 390 20 3. 30 4. 26 11.1 2. 53 2.6 22.8 2. 54 2. i) 22. 8 7. 9 0. 876 0. 775 129. 0 12 15.9 20. 5 56. 5 3. 500 3. 554 20 3. 18 4.10 11. 3 2. 38 4. 0 23. 5 2. 35 3. 6 23.5 6.5 0.851 0.753 132. 8 13 14. 5 18.8 56. 3 3. 883 3. 877 25. 6 3. 72 4. 82 14. 4 2. 32 4. 5 30. 4 2. 40 5. 4 30. 4 5. 6 0. 842 0. 745 134. 2 14 17. 2 22.2 58. 5 3. 340 3. 390 Z) 3. 44 4. 44 11. 7 2. 48 2. 7 23.5 2. 53 2. 7 23. 8 8.8 0. 840 0.743 134. 6 Ce Dihydro. 18.2 23.5 49.2 2.702 2. 584 33 7 6. 25 7.90 16.6 3.30 0.2 30.3 2.39 4.6 29.1 6.3 1.147 1.010 09.0 Ale. Wash. Dihydro phosphate-. 18.9 24.4 49.5 2.616 2.584 Z) 0 3.78 4.88 9.9 3.70 0.0 18.4 2.36 2.9 17.7 6.1 1.130 1.000 100.0

Composition `#l0 represents substantially l HsPOi-MnOLPOm-IM Hi8.

Composition #11 represents substantially 5% HsPO4-l\In(HsPOi)z-1l H 2 Composition #l2 represents substantlallyM HIPOvMntHzPOi-ll H10.

Composition #13 represents substantially HsPOi-MMHiPOi) 14% H10.

Composition #14 represents substantially 9g HIPOi-MnOEIiP 00H4 H10. Centrit Dlhydro." =Mn(HiPO4)r2H1O crystals prepared by iractional crystallization per existing patent disclosures and centrifuged to separate from maior part of mother liquor.

Alc. Washed Dihydrophosphate=Centrlt. Dihydro." which was washed carefully with ethyl aleohl to remove` the adsorbed mother liquor.

Alter Digesting =the initial solutions were maintained at 2))- m8 F. for 4-5 hours.

Solids" in the headings oi the columns refers to the compounds cited in column #1.

assesses Percent of Av. Comp. Gms. Pptd Percent of vMangatlous G'ms; Solids Original oi:Pp't. by Digestion Loss from Phosphate Oom- Pptd by Wt. of Dis- Digestion pound Digestion ssollrird o s l Mn P205 Mn P205 Mn P205 0.81- 4.07 O. 30 0.31 9.`0` 2.9 0.1-3 0.65 0. 05 0. 05 1. 5 0. 4 o o o oo 0 0 0 0 0 0 O 0 0- l)` gihgdro-; 5. 56 16.5 2.07 2,-14 33.1 12.9 Alct Was i .Y l I hydro 1 3.53 17.6 1.31 1.35 39.3 13.7

losses found when the cited heated to the operating tern- This` 'table tabulates 'the illustrative solutions 'were perature range.

Recognizing the limits of accuracy 'of 'conventional analytcal methods for the* determination of manganese and phosphorus, point' a,." Fig. 2, issubstantially ity of the novel drymangnous phosphate compound'so'f the present invention is also illustrated with respect to free acid and total a'cid;fwith respect to pH ascomp'ared to known compounds; with respect 'to manganese conce'n'# tration atvarious temperatures as l compared 'to kno'v'vh c'onipounds;` and with; respect to' P205 concentrations at various temperatures.

The following table illustrates' thevweigh't ratios ofthe' components offthe 'novel `d'ry rnanganousV phosphate conn' pounds o'f this invention:

TABLE III Weight rlatos and 'Scan' be called' dima'nganousy henidecahydropenraorthophosphate pentahydrate, while point b is` correspondingly the monohydrate. The hydrates of this salt are suhcientlyrieh in. manganese to provide a moderate buffering effect when introduced into coating baths overly rich in acidity;

Point d, Fig. 2, is substantially 'ifi-SPO? Mn(fH2PO`4.)' "2 Fig-Q- and cani-be'fnarned "manganou`s heptahydrotriorthophosphlte hemipentahydrate, while point c would be the quarter or tetraliydiate; these compositions are sufficiently rich in .phosphoric *acid in respect to manganese to-supply a moderate a1nount-of-excessf 'free acidity 'which may' loe-desirable and-useful where films-'of rust must be removed concurrently with the deposition of protective coatings. Of particular interest is vthe compositionA shown in Table. IH;` and 'illustrated by compound 12; these compounds may. be written and may be named tetrarnanganous pentacosih'ydrohenidecaorthophosphate (dito deca) hydrate; these compounds dissolve in Water to provide the optimum ratio of manganese to phosphoric acid for the preparation and maintenance of manganous phosphate coating baths.

The data set out in Tables II and II-a illustrates the economies available in the use of the compositions of the present invention as compared to prior art manganous compounds, usually Mn(H2PO4)2-2H2O, in the quantities required to produce unit point total acidity. The stabil- A thirty point manganous phosphate solution made from dihydrogen phosphate'crystals prepared according to the prior art will hydrolyze to some 'extent'i'the coldl When a solution ofthisphosphate is heated to prepare it for the coating operation a considerable quantity ofprecipitate is formed which is entirely insoluble and amounts to approximately-31% of thel manganese and 12.9% of the P205A originally introduced linto the bath.- Thus the bath 'undergoes a Vradicalchange in character. A thirty point solution prepared with a -dry -manganous phosphate compound of the .present i-nventionfis completely soluble, does not hydrolyze-when heated to prepare the solution as acoating bath and the bath remains clear. Asshown vin-Tables Il and iba, baths ranging between 2() andw25 points also exhibit the same characteristics. yIn connectionfwith these solutions'it is to be understood that theyterm point means the number of milliliters of 0.1 normal sodium hydroxide required lto' titrate a 10.0 ml. sample of the bath to the phenolphthal. ein end point; TheA two solutions are substantially'the same chemically after'heating but a coating' bath` can" be maintainedwith less of the-compounds of the present inventionon a weight basis as compared tothe' dih3ldz-o-l genpho'spha'te'compounds"of'theprior art in the app'ro'it'imateratio of 75 to Y100.

After using the baths for identical coating operations it is found that the loss of manganese in the sludge resulting from the operation of the bath employing the manganous phosphate compounds of the present invention is 23% of the loss from the bath employing manganous dfhydrogen orthophosphate prepared according to the prior art. The loss of P205 in the sludge found in the bath of the present invention is 42% of that lost from the prior art dihydrogen orthophosphate bath. Comparing the weight of sludges formed during the operation of the baths it is found that the bath employing the compounds of the present invention contains a sludge which is 42% by weight, dry basis, of that found in the bath em ploying the manganous phosphate of the prior art.

The coating baths were conditioned by treating eight successive panels in each bath before the data was collected to obtain the results discussed above. The coatings on the panels from the bath utilizing the manganous phosphate compounds of the present invention are uniform in appearance and in weight for all of the panels throughout all of the cycles while the coatings provided by the bath of manganous dihydrogen orthophosphate prepared in accordance with the prior art deteriorate in quality as the test progresses. It is also found that there is less etching or attack on the surface of the panels being coated by the bathmade up from the compounds of the present invention.

After the above solutions had been conditioned by treating the equivalent of 10 square feet of standard test panel surface per gallon, a series of three panels was treated in each bath for one hour per panel and the baths were brought back to a 30 point ,strength previous to each treatment. `All 'three panels treated in the coating bath prepared from the material of the present invention were uniformly coated, while the coating on the second and third panels treated in the bath prepared from manganous dihydrogen phosphate prepared according to prior art was very inferior to that on the first panel. Table IV summarizes the averaged coating data.

Panels coated from baths employing the manganous phosphate compounds of the present invention may be tested by the method described by Andrews et al. in Journal of Applied Chemistry, volume 4, pages 581-595, of November 4, 1954, and the protective properties of the coats may be compared by the copperspot test as reported by Akimov et al., USSR Academy of Sciences, Moscow, 1946, page 117. These tests show that manganese phosphate coats obtained from solutions in accordance with the present invention are more uniform than those of the prior art; that more manganese phosphate is availablein the solutions for coating and that more manganese phosphate is recovered as useful coating material; and the copper spot test shows that panels coated from solutions of the present invention are substantially completely protected.

It should now be apparent that the present invention in every way satisfies the several objectives described above.

Changes in or modifications to the above described illustrative procedures and compounds may now be suggested to those skilled in the art without departing from the present invention. Reference should therefore be had to the appended claims to determine the scope of the present inventive concept.

What is claimed is:

l.l Dry acidulous water soluble manganous phosphate compounds consisting of approximately 18.0-23.3% MnO, approximately 51.6-60.7% P205 and approximately 18.7- 28.1% H2O in ymolar ratio of from one mole of manganous oxide and from one and one-quarter to one and one-half moles of phosphorous pentoxide and from three and one-quarter to six moles of water of which from onehalf to two' and one-half moles of water is present as water of crystallization.

2. Dry watersoluble acid salts of manganous phosphate -compounds consisting of manganous dihydrophosphate containing as the acid of crystallization condensed anhydrous orthophosphoric acid in the ratio of from one-half mole to one mole of orthophosphoric acid per `mole of manganous dihydrophosphate and including one-half to two and one-half moles of water of crystallization.

3. Dry water soluble acid salts of manganous phosphate compounds having the empirical formula H7Mn(PO4)3(1/21/)H2O and weight ratios P2O5/Mn=3.876, P2O5/Mn0=3.00 and P2O5/H2O=2.951.97.

4. Dry water soluble acid salts of manganous phosphate compounds having the empirical formula H2sM114(P04)11 (2-10)H20 and weight ratios P2O5/Mn=3.554, P2O5/Mn0=2.752 and P2O5/H3O=2.991.92.

5. Dry water soluble acid salts of manganous phosphate compounds having the empirical formula and weight ratios P2O5/Mn=3.390, P2O5/Mn0=2.625

and P2O5/H2O=3.011.91.

6. Dry water soluble acid salts of manganous phosphate compounds having the empirical formula and weight ratios P2O5/Mn=3.230, P2O5/Mn0=2.502 and P2O5/H2O=3.02l.83.

7. Dry water soluble acid salts of manganous phosphate compounds having an empirical formula References Cited in the le of this patent UNITED STATES PATENTS 2,310,239 Jernstedt Feb. 9, 1943 2,516,008 Lum July 18, 1950 2,516,139 Mazia July 25, 1950 FOREIGN PATENTS 365,569 Great Britain Printed 1932 447,918 Great Britain May 27, 1936 OTHER REFERENCES Mellor: Comprehensive Treatise on Inorganic and Theoretical Chemistry, vol. 12, pages 451, 452, published 1932. Copy in Sci. Lib.

UNITED STATES PATENT GFFICE Certicate of Correction Patent No. 2,866,728 December 30, 1958 Warren D. VVarinner It is hereby certified that error appears in the printed Specification of the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 3, line 32, for liming read -1i1niting; columns 3 and 4, Table II, twelfth column thereof, fourth item under the subheading Free, for 4.5 read 5.4.; in the footnote at bottom of same page, third line from the last, for alcohl read -a1coho1.

Signed and sealed this 28th day of April 1959.

[SEAL] Attest T. B. MORROW,

Attestz'ng Ocer.

ROBERT C. WATSON, Commissioner of Patents. 

7. DRY WATER SOLUBLE ACID SALTS OF MANGANOUS PHOSPHATE COMPOUNDS HAVING AN EMPIRICAL FORMULA 